/Engine/Source/Developer/TextureBuild/Public/TextureBuildFunction.h
This function does the meat of breaking out the inputs from the build context and handing them to the tiler, then packing them back up for the build process.
void GenericTextureTilingBuildFunction ( [UE::DerivedData::FBuildContext](API\Developer\DerivedDataCache\FBuildContext) & Context, const [ITextureTiler](API\Developer\TextureFormat\Interfaces\ITextureTiler) * Tiler, const [UE::DerivedData::FUtf8SharedString](API\Developer\DerivedDataCache\FUtf8SharedString) & BuildFunctionName )